Azalea Sawfly

Azalea Sawfly

Identification: Two species attack azalea in Tennessee: Abia sericea (azalea sawfly) and Atomacera decepta (azalea leaf-mining sawfly). Larvae of A. sericea are greenish with a dark head, up to 18 mm, feeding gregariously on the leaf margin. Adults are wasp-like, 8–10 mm, with orange-yellow markings. Host-specific to azalea (Rhododendron spp.) and rhododendron. The gregarious feeding habit and specific host distinguish azalea sawfly larvae from caterpillar defoliators on the same host.

Life cycle: One to two generations per year in Middle Tennessee. Overwinters as pupae in the soil beneath host plants. Adults emerge in May; females deposit eggs in leaf tissue along margins. Larvae hatch and feed gregariously, initially notching leaf margins and progressing to complete defoliation of individual shoots. Mature larvae drop to soil to pupate; a partial second generation may occur in August.

Damage signs: Characteristic notching along leaf margins from early-instar feeding, progressing to complete consumption of leaves from the tip inward. Groups of larvae on a single shoot can fully defoliate an azalea branch tip within days. Azalea sawfly defoliation tends to occur in isolated branch patches rather than the whole-plant pattern of whitefly or lace bug damage. Plants lose aesthetic value rapidly but typically recover if damage is limited to one or two events per season.

Treatment window: May through early June when first-generation larvae are young and gregarious. A second window in August for any second-generation larvae.

UT-recommended approach: Hand-removal of larval colonies by clipping and destroying infested shoot tips is effective and targeted on accessible specimens. Spinosad or insecticidal soap applied at first larval appearance targets gregarious young instars. Avoid treating azaleas in bloom. Systemic imidacloprid is less effective against sawfly larvae than against sucking pests — sawflies are Hymenoptera and have different susceptibility profiles than Lepidoptera and Hemiptera; contact insecticides or spinosad are the appropriate chemistry for this pest.